When selecting a shower door, carefully measure the distance between the two walls and make sure you allow for your tiles. Then, choose one with an adjustment that covers the calculated gap. It's also worth checking both the top and bottom of the recess, in case one or both of your walls are out of true. All doors allow for some adjustment. With aluminium frame models, the adjustment is usually quite a big range as generally it can be done on both sides. Getting the perfect fit is achieved using two aluminium uprights - the first is a U-shaped profile, which screws to the wall; the second being the aluminium frame of the door itself, which is a reverse U-shape. By sliding one over the other an alterable fitting is formed.
With the Mirabella frameless designs the door is fixed to the wall in a different way - using solid brass brackets. There is adjustment within the brackets but this is less than would be achieved with aluminium profiles. In the case of Mirabella the maximum leeway is around 15mm, and for this reason there are more size options (A and B versions of each size), so check the size of the gap carefully. Note also that Mirabella shower doors require a solid or reinforced wall, as all the weight of the glass is borne by the two brackets on each side; whereas aluminium profiles are fixed to the wall in several places - and therefore generally suitable for an unsupported stud wall.